TECHNOLOGY AREA(S): Sensors, Electronics, Battlespace
OBJECTIVE: Pyramid Wavefront Sensor (PYWFS) is a highly sensitive sensor compared to the Shack-Hartmann wavefront sensor (SHWFS). We want to design and build a three-sided PYWFS as it is very difficult to build a four-sided PYWFS.
DESCRIPTION: Wavefront sensing is one of the key elements of an Adaptive Optics System. Though the Shack-Hartmann Wavefront Sensor (SHWFS) is most commonly used for astronomical applications, the high sensitivity and large dynamic range offered by the Pyramid Wavefront Sensor (PYWFS) allows us to observe in adverse seeing conditions and sense atmospheric turbulence at the sensitivity limit imposed by physics. However the person who built most of the conventional four-sided PYWFS has retired and it is mechanically easier to build a three-sided PYWFS. Through this STTR we want to test the feasibility of a three-sided PYWFS, design and build a three-sided PYWFS, develop a reconstructor for it, and compare it to the current state-of-the-art SHWFS. Successful bidders will to the greatest extent possible show: 1. Theoretical calculations to obtain wavefront gradients from a three-sided pyramid sensor. 2. Ability to develop a reconstruction algorithm to convert gradients to a reconstructed wavefront. The reconstruction algorithm shall be detailed and described. 3. Understanding of the differences between a modulated and fixed PYWFS. 3. Ability to come up with and justify a WFS performance metric, be it strehl, contrast, point spread function size and encompassed energy, or something else. 4. Ability to accurately model a three-sided PYWFS, a four-sided conventional PYWFS, and a SHWFS and demonstrate wavefront reconstruction with all three sensors. Compare the simulated performance of the three sensors 5. Ability to provide an opto-mechanical design for the three-sided PYWFS. 6. Ability to physically build a three-sided PYWFS. 7. Ability to set up a laboratory demonstration in which the three-sided PYWFS is compared with a SHWFS by using a laser/bench source. 8. Ability to integrate the three-sided PYWFS with an AFRL/RDS telescope. 9. Understanding of the cost of hardware and software, as well as the people-hours and time required to design the three-sided PYWFS and its reconstruction algorithm. 10. Ability to provide follow-on use by the Air Force under a cooperative agreement to be arranged in the future.
PHASE I: Demonstrate theoretically and through simulations that gradients can be obtained from a three-sided PYWFS from which a wavefront can be reconstructed. Formulate an optical design for the three-sided PYWFS.
PHASE II: Build a three-sided PYWFS based on the optical design presented in Phase I. Develop a reconstructor for the three-sided PYWFS. Compare the simulated performance of the three-sided PYWFS with the four-sided PYWFS, and the SHWFS. Set up a laboratory experiment to compare the performance of the three-sided PYWFS with the SHWFS. The laboratory demonstration may be done with government help. At effort close, propose cooperative agreement to make sensor available to Air Force.
PHASE III: With government help integrate the three-sided PYWFS on an AFRL/RDS telescope. Compare the performance of the three-sided PYWFS against a SHWFS with a bench source and on-sky. Provide a final report detailing the design and construction of the three-sided PYWFS, and its comparison with the SHWFS.
1. Esposito et. al. First Light Adaptive Optics Systems for Large Binocular Telescope. SPIE. 4839. 164E, Feb 2003.
2. Hadi et. al. Development of a Pyramid Wavefront Sensor. AO4ELT3.13429, May 2013.
3. Kopon, D. Enabling Technologies for Visible Adaptive Optics: The Magellan Adaptive Secondary VisAO Camera. SPIE Proc. Vol. 7439, Aug 2009.
4. O. Guyon. Limits of Adaptive Optics for High-Contrast Imaging. ApJ, 629:592“614, August 2005.
KEYWORDS: Wavefront Sensors, Pyramid, PYWFS, Reconstructor, Reconstruction Algorithm, Adaptive Optics